The use of light sent through optical fibers for the transmission of information is now in general acceptance as being technically feasible, reliable, and economical. Diversity of application and ever-lengthening time of in-service experience have defined various deficiencies to date in manufacture and place of service of cables. Other deficiencies relate to various degrees of cable production, insulation, and usage.
A major factor in overcoming cable deficiences and maintaining cable integrity during production, packaging, installation, and operational service, is ruggedization. "Ruggedization" refers to strengthening and protecting of the optical fiber to increase resistance to wear, stress, and general abuse inherent in field-handling and usage. If optical fibers are not suitably ruggedized, they are fragile and susceptible to major increases in signal attenuation, as well as breakage. In addition, cables of conventional design have presented problems in coiling, particularly for high-density packaging. Proper ruggedization is therefore important to any cable design. There is also increasing recognition of the merits of using a cable made of dielectrics as compared to metals.
The present invention is therefore directed to the development of ruggedized optical fibers of substantially dielectric construction, which fibers enjoy the benefits of immunity from increased signal error due to stresses caused by ambient electric fields, and even burn-out from lightning and electromagnetic impulses. In addition, the optical-fiber cables of the instant invention are metal-free and most difficult to detect.